It is known in the art to manufacture airfoils and platforms of blading members of fluid flow machines separately and to assemble a blading member from airfoil members and platform members. This offers various benefits, e.g. different materials may be used for the airfoil and the platform, complexity of the individual pieces is reduced, thus allowing for more complex cooling schemes, and in providing individual geometries more suitable for casting or machining. However, airfoils and platforms need to be joined properly and reliably.
EP 1 176 284 proposes joining airfoils and platforms by brazing. This results in the individual pieces being rigidly joined to each other and may lead to high thermal mismatch stresses. Moreover, separation of the pieces for reconditioning is difficult.
U.S. Pat. No. 5,797,725 discloses blading members wherein each of the airfoil and the platform comprise a corresponding flute which are filled by a common retainer. In a preferred embodiment the retainer is manufactured inside the flutes by casting. Joining the components according to this document requires extensive manufacturing steps. Also, due to the proposed casting step, limitations are implied with respect to the choice of materials for the retainer, the platform member and the airfoil member.
U.S. Pat. Nos. 7,686,571 and 7,704,044 propose coupling airfoils and platforms applying a mechanical interlock element, wherein said mechanical interlock element is slidably received inside flutes provided in the platform and along the pressure or suction side of the airfoil. The applicability of the connection is quite limited as not every mechanical interlock shape can be slidably pushed into the flutes. Furthermore, as curved retainer elements, resembling the curved shapes of the airfoil pressure and suction side, are completely received within the platform and are only accessible from front sides, it might be extremely difficult to remove the interlock members for servicing, inspection and reconditioning purposes, in particular if during operation an interlock element has seized up in a locking flute.